*Purpose: Our laboratory performs STAT HLA typing for an OPO using RT-PCR methodology. A 46 year old, male Caucasian deceased donor was worked up by our laboratory. The Class II typing that was obtained was DRB1*01/DQB1*05, DRB1*07/DQB1*02, DRB4 and DRB4 Null. Based on DRB1 and DRB3/4/5 associations, the DR53 antigen should be expressed however, the DRB4-Null allele was detected by molecular methods. The donor was allocated as DR53 Negative however, a more in-depth workup was required for further elucidation of the antigen.

*Methods: The donor was typed using the following molecular platforms: (i) RT-PCR (Linkage BioSciences and CareDx), (ii) RSSO, One Lambda, and (iii) NGS, Illumina. In addition, HLA frequencies were reviewed.

*Results: Table 1 shows the HLA typing of the donor with different typing methodologies and vendors. Organs were allocated as DR53 Negative based on the results obtained from Vendor 1. The following business day, the donor was typed using RSSO methodology. Again, the Null and antigen was detected. A secondary RT-PCR kit was run (Vendor 2) and DR53 Null was obtained. All Low-Intermediate typing results hinted the presence of DRB4*02:01N as the DR53 Null allele. Research was performed to find other cases like this. The following websites were reviewed for reported typings: Allele Frequency Net Database, IPD-IGMT/HLA Database, HaploStats Be The Match Database. No reports of DRB1*07/DQB1*02/DRB4*02:01N (DR53N) were found for either Caucasians or all ethnicities in the databases. Upon further investigation it was determined that these databases do not have haplotype nor allele frequencies for DRB4 Null alleles. Therefore, it is unknown how frequent DRB4 Null alleles are present in all populations. The sample was sent to a reference laboratory for Next Generation Sequencing and a DR53 ambiguity was reported. Upon further resolution, a result of Null (DRB4*02:01N) was obtained.

*Conclusions: This is the first case the authors can find in which both the Null and expressed antigen DNA was detected. For STAT allocation, instances like this case present a challenge for accurate typing when limited hours present. Reporting false antigens will limit organ offers to sensitized patients. Patients with DR53 antibodies would have been eliminated from this donor offer. Laboratories need to have (I) policies for antigen determination when rare ambiguities exist and (ii) multiple methods available for STAT typing to ensure organs are allocated correctly. This will aid in the avoidance of unneeded cold ischemia time should unexplained positive crossmatch results be obtained due to incorrect typing.

« Back to 2019 American Transplant Congress